1. FIELD OF THE INVENTION
The invention relates generally to an arrangement for determining the position or travel of a piston in hydraulic, pneumatic or hydro-pneumatic assemblies, such as vibration dampers, gas springs and hydro-pneumatic suspensions, and more particularly, to vibration dampers having the piston arranged to slide axially by means of a piston rod in a cylinder filled with at least one damping medium.
2. DESCRIPTION OF PRIOR ART
Suspensions are, for example, known from British Laid-Open Patent Application No. 8110972 and its corresponding German Laid-Open Patent Application DE-OS 32 12 433 in which each suspension unit of a vehicle has a sensor for adjusting its platform height producing an output magnitude which changes progressively with the platform height. The drawback here is that for adjusting the height of the platform, i.e. the spacing between the sprung and unsprung parts of the vehicle, a platform height sensor is provided at each respective suspension unit. Such a device is particularly expensive as the corresponding measured values between the vehicle suspension and the actual suspension unit or strut must be ascertained. Further, this determination of the measured value is expensive as corresponding measurement transducers must be provided on the widely different parts of the vehicle.
3. OBJECTS OF THE INVENTION
Taking the above as a starting point, it is the object of the invention to provide a method of measuring the piston travel, the apparatus of which operates without physical contact between the parts of the transducer thereby providing with a high degree of reliability. It is a further object of the invention to integrate the measuring arrangement into the suspension of a vehicle, which arrangement has relatively small dimensions with respect to its incorporating unit and thereby requires no major modifications to existing hydraulic, pneumatic or hydro-pneumatic assemblies such as vibration dampers, gas springs and hydropneumatic suspensions.